1. Field of the Invention
The present invention relates to a microscope having an autofocus device.
2. Description of the Related Art
The autofocus devices employed in microscopes in the known art include image contrast-type autofocus devices (AF devices). Such an AF device moves a specimen stage along the up/down direction (z axis) while detecting the contrast of a captured image and sets the Z coordinate at which the largest contract value is achieved as the focused position. The AF device then moves the stage to the detected focused position and completes the focusing operation.
Generally speaking, the range over which high contrast is achieved is extremely small relative to the range along the Z axis over which the AF device moves the stage (the search range) in order to detect the contrast of the captured image. Since it takes a considerable length of time to move the stage over the search range, it is difficult to reduce the length of time to elapse following the AF operation start until the stage is moved to and stopped at the focused position. If, on the other hand, the search range is greatly reduced so as to reduce the length of time required for the AF operation, the focus range may not be contained within the search range, depending upon the specimen.